Industrial plants, agricultural installations, hospitals, kitchens, etc. that handle large quantities of organic material such as hog farms, dairy farms, chicken farms, meat packing plants, animal rendering plants, composting plants, paper mills, sewage treatment plants and other similar installations can generate large quantities of odors that typically exit the facility in an odor contaminated atmospheric effluent (flume) or other effluents. Such an effluent can contain a large variety of odoriferous or odor causing inorganic and organic chemicals or molecules including organic sulfides or organic thiols (mercaptans), monoamines, diamines, triamines, ammonia, alcohols, formaldehyde, acetaldehyde, carboxylic acids, skatole, carbon disulfide and hydrogen sulfide and other odor forming oxidizable compounds. An atmospheric effluent having one or more of such compounds can have a strong odor and can be highly objectionable within the plant to plant personnel and outside the plant to plant neighbors.
An odor is a gas phase emission that produces an olfactory stimulus. The odor thresholds of many chemicals that act as odor compositions common throughout the chemical process industries include, for example, ethyl sulfide having an odor threshold in the atmosphere of 0.25 parts per billion (ppb), hydrogen sulfide with an odor threshold of 0.4 ppb, dimethyl sulfide with an odor threshold of 1.0 ppb, ethyl mercaptan with an odor threshold of 1.0 ppb, methyl mercaptan with an odor threshold of 1.1 ppb. With a low threshold a small amount of these and similar odors common in plant effluent are serious olfactory problems. Such odors result from processing large quantities of organic materials and are generated by the action of micro-organisms in any biologically active system on a source of organic material producing the odors. There are many other odor producing chemicals possible, however, as shown in this representative, non-inclusive Tables 1 to 3:
TABLE 1 Sulfur compounds Hydrogen Sulfide Thiophene Carbonyl Sulfide Isobutyl Mercaptan Methyl Mercaptan Diethyl Sulfide Ethyl Mercaptan n-Butyl Mercaptan Dimethyl Sulfide Dimethyl Disulfide Carbon Disulfide 3-Methylthiophene Isopropyl Mercaptan Tetrahydrothiophene tert-Butyl Mercaptan 2, 5-Dimethylthiophene n-Propyl Mercaptan 2-Ethylthiophene Ethyl Methyl Sulfide Diethyl Disulfide
TABLE 1 Sulfur compounds Hydrogen Sulfide Thiophene Carbonyl Sulfide Isobutyl Mercaptan Methyl Mercaptan Diethyl Sulfide Ethyl Mercaptan n-Butyl Mercaptan Dimethyl Sulfide Dimethyl Disulfide Carbon Disulfide 3-Methylthiophene Isopropyl Mercaptan Tetrahydrothiophene tert-Butyl Mercaptan 2, 5-Dimethylthiophene n-Propyl Mercaptan 2-Ethylthiophene Ethyl Methyl Sulfide Diethyl Disulfide
TABLE 1 Sulfur compounds Hydrogen Sulfide Thiophene Carbonyl Sulfide Isobutyl Mercaptan Methyl Mercaptan Diethyl Sulfide Ethyl Mercaptan n-Butyl Mercaptan Dimethyl Sulfide Dimethyl Disulfide Carbon Disulfide 3-Methylthiophene Isopropyl Mercaptan Tetrahydrothiophene tert-Butyl Mercaptan 2, 5-Dimethylthiophene n-Propyl Mercaptan 2-Ethylthiophene Ethyl Methyl Sulfide Diethyl Disulfide
Attempts have been made to reduce the production of the odor compounds and to reduce the release of the odor compounds from plants. Robinson, "Develop a Nose for Odor Control", Chemical Engineering News, October 1993 contains a generic disclosure of odor problems and conventional odor control using aqueous treatment compositions including H.sub.2 O.sub.2, FeCl.sub.3, KMnO.sub.4, NaOH and others. Careful control over the organic materials within the plant and reduction of microbial populations within the plant have been attempted to reduce the generation of the odor compounds in the plant atmosphere. Attempts to scrub the odor compounds from the plant atmosphere have been made using a variety of simple absorptive and oxidizing scrubbing materials. Fragrance chemicals that simply mask the offensive odors have been tried. In fact, essential oils have been used previously as odor masking compounds.
Sodium hydroxide (NaOH), activated carbon are useful absorptives. Oxidizing materials such as ozone (O.sub.3) have been used. Halogen oxidants including chlorine dioxide (ClO.sub.2), sodium hypochlorite (NaClO) and others have been attempted. Some degree of success has been achieved using these oxidative materials to remove organic odor molecules from atmospheric effluents. While chlorine dioxide has had some success, chlorine dioxide is highly toxic, difficult to handle and must be generated on site. Such difficulties lead to substantial resistance to its use. Further, hydrogen peroxide is also known for odor control. Hydrogen peroxide by itself is not effective against a broad range of odor constituents without additional treatment materials. However, the application of oxidative technologies including ozone, hydrogen peroxide, chlorine dioxide and other oxidants have had some limited success. Chlorine and hypochlorite are commonly used but have drawbacks and are corrosive.
The use of peroxyacid materials in microbiological methods are also known. For example, Grosse-Bowing et al., U.S. Pat. Nos. 4,051,058 and 4,051,059 disclose peroxyacetic containing antimicrobial compositions. Stas et al., U.S. Pat. Nos. 4,443,342 and 4,595,577 disclose the treatment of waste water and waste gases containing dialkyldisulfides by metal catalytic oxidation of these compounds by means of a peroxide compound in an aqueous medium. Lokkesmoe, U.S. Pat. No. 5,409,713 teaches peroxyacetic materials as microorganism sanitizers or growth inhibitors in aqueous transport systems typically containing produce and large amounts of challenged soil load.
Fraser, in "Peroxygens in environmental protection", Effluent and Water Treatment Journal, June 1986 disclose that hydrogen peroxide (H.sub.2 O.sub.2) can be used to reduce odor. Fraser only discusses microbial control with peroxyacetic acid and does not correlate odor control to peroxyacid treatment or concentration. Littlejohn et al., "Removal of NO.sub.x and SO.sub.2 from Flue Gas by Peroxyacid Solutions", Ind. Eng. Chem. Res. Vol. 29, No. 7, pp. 1420-1424 (1990) disclose peroxyacids in removing nitric oxides and sulfur dioxide from coal fire derived flue gas.
Peroxyacetic acid, neat and in aqueous solutions containing peroxyacetic acid has a strong pungent oxidizing odor resembling but stronger than acetic acid. Such =materials have not been seriously considered as odor reducing materials because of the nature of its odor. The concern being that in any treatment process using a significant amount of peroxyacetic acid, the resulting treated effluent would inherently obtain the pungent odor of the peroxyacetic acid. Further, peroxyacetic acid solution inherently contain large amounts of acetic acid (HOAc).
Essential oils are known aromatic substances and have pleasant masking odors. However, many oxidizing compounds are adversely impacted by the presence of essential oils. Generally, the oxidizing agent is presumed to act to oxidize the essential oil, thereby causing the mutual destruction of their functional abilities. Because of the reactivity the art has avoided using essential oils with oxidizing agents. Consequently, there remains a need for enhanced odor reduction processes which are able to take advantage of the beneficial effects of essential oils without causing excessive damage to the oxidizing systems.